The Difference Between Class A and Class AB Tube Amps

You’ve seen various tube amp descriptions that read Class A or Class AB amplifier, but what does any of that mean? And why should you care?

KT88 Tubes

What’s the difference between class A and class AB tube amps?

Check out this break down of the differences for the quick answer. The detailed explanation and some examples follow further on….

Class “A” Amplifiers

Advantages:

  • The tube always warmed up and ready to amplify the signal.
  • Tube does not have to “wake up” from a “ready” state.
  • Class “A” amps have greater output than Class “AB” amps. If two EL84 output tubes in a Class A design may produce only 10 watts of output power, then the same two tubes in a Class AB design might produce 50 watts.
  • Smooth compression.
  • Less headroom. (NOTE: This is a disadvantage to some musicians who are looking for good, clean tone at higher volumes).
  • More responsive to the touch – i.e.: feels good to play.
  • Class A amps with EL84 tubes in push-pull design emphasize high order harmonics. This emphasis makes the amp “sing”.

Disadvantages:

  • Keeping the tubes warmed ready requires more current at all times. This constant current leads to shorter tube life.
  • Lower power rating than a Class “AB” amp with the same tube configuration.

 Class “AB” Amplifiers

Advantages:

  • Longer tube life.
  • More headroom – cleaner cleans at higher volume.
  • Tighter bass response – less prone to “muddy” tone.
  • More efficient use of power.

Disadvantages:

  • Not as responsive as a Class “A” amp.
  • Tone won’t “break up” as easy.

Class A vs Class AB, the Detailed Explanation.

The three major parts that make an amplifier tube are: the Cathode, the Grid and the Plate. The Cathode heats up when voltage hits the tube, causing a cloud of electrons to form. The Plate has a positive charge, which causes the negatively charged electrons to flow toward it. The Grid controls this flow of electrons. It is also the audio signal input for the tube.

An audio signal entering the tube causes a change in voltage at the Grid. This change in voltage changes the flow of electrons  and causes amplification.

The behavior of electrons described above is an example of a Class A amplifier. These amps apply a positive voltage to the Grid. Class AB amplifiers apply a negative “bias” voltage to the grid. This bias causes the electrons in the cloud to avoid the Plate. This is the standby mode of the tube.

The voltage of the audio signal entering the Grid causes the voltage on the Plate to change from negative to positive. This attracts the electrons in the cloud and causes them to flow to the plate. The tube in the Class AB amp then behaves like a Class A described above.

The need to change the charge of the plate from positive to negative causes the Class AB amplifier to feel less responsive than a Class A amp. But it also means the tube components aren’t in full use even when a signal is not passing through. This means the tubes generally last longer.

Class A amplifiers

Bugera V5 Infinium

Looking for a low watt amp that won’t blast a hole in your eardrums or your budget? Bugera is for you.

The Bugera V5 Infinium is a 5 watt all tube amp for less than $200.

Let that sink in for a moment.

For the price of a really good solid state amp, you can get an all tube amp. But that’s not all.

  • The Bugera V5 is a Class A amp driven by a single EL84 tube with a single 12AX7 tube in the preamp.
  • Specially designed 8 inch Turbosound speaker. (This is a classic combination for the British crunch and buttery blues tone)
  • Power attenuator, which effectively lets you decrease the headroom even more and get killer overdrive or distortion at a lower volume
  • Digital reverb capable of dialing in everything from subtle to downright cavernous.

Where the Bugera V5 Infinium really makes its mark is with it’s Tube Life Multiplier technology. According to Bugera, this tech ensures:

.. greater reliability and consistent tone over the lifespan of your tubes by monitoring the performance of each of the amplifier’s output tubes and maintaining them at their ideal operating point for an evenly distributed load.

There’s also an LED next to each tube that lets you know when it’s about to die.

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Ibanez TSA5TVR

This stylish little beast is another micro amp, 5 watts and an 8-inch speaker… and a built-in Tubescreamer circuit!

With a retro look of a 1950’s television it harkens back to a simpler age when televisions were the furniture centerpiece in a room; meant to attract attention and start a conversion. The Ibanez TSA5TVR is an attention-getter as well.

  • 8″ Jensen C8R speaker.
  • Ruby 6V6 and 12AX7 tubes.
  • Lush Accutronics spring reverb
  • Built-in Tubescreamer – complete with overdrive, tone, and level knobs

The TSA5TVR gives you everything from slight, dirty gain for blues and rock all the way up to high gain for lightly compressed distortion. It’s a small package that sounds much bigger.

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Peavey ValveKing Royal 8

The ValveKing gives you punchy dynamics and classic rock tones that sound much larger than its small package.

  • 5 watts
  • One EL84 output tube
  • One 12AX7 preamp tube
  • Single-channel design
  • Dual ¼” inputs
  • Master volume and gain controls

Rollback the gain and crank up the master volume to get that great class A “breakup” power-amp tone. Or crank the gain and dial back the master volume and you’ve got raging  preamp distortion.

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It’s that easy.

Orange Tiny Terror TT15C-12

This loud and proud Orange Terror owes it’s punch to a special reissue of the Celestion G12H 12 inch speaker. The G12H is a mix of the Vintage 30 and Greenback speakers and produces thick, warm and sugary sweet tones.

  • 15 watts, Switchable to 7 watts
  • Single Celestion G12H 12″ Speaker
  • Gain, tone, volume controls
  • 2 x EL84; 2 x ECC83/12AX7 tubes

The cool thing about the TT15C is that it’s switchable from 15w to 7w, which makes it great for break up or recording.

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Class AB amplifiers

Vox Night Train NT15C1-CL

 

The Night Train is a big sounding Class AB amp covers all the Vox tones from clean to crunch and all the way to high-gain. The classic Vox look with suitcase style handles makes the package complete.

  • 3 – 12AX7 tubes in the preamp section
  • 2 – EL84 tubes in the power section
  • Two-channel BRIGHT/GIRTH
  • The THICK switch provides an additional gain boost on the BRIGHT channel
  • Reverb
  • 15 Watts
  • 12 inch Celestion G12M Greenback speaker
  • Inputs/Outputs: Guitar Input, FX Send, FX Return, Foot switch
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Marshall DSL15C

The DSL15C is Marshall’s 15w, all tube combo amp. It’s compact, but packs a punch with classic EL84 tube tone. The DSL15C has two 6L6 tubes in the power section, but the preamp is all EL84s.. three of them to be exact.

15 watts may not sound like a lot, but for a tube amp it’s plenty loud for practice or small gigs. In fact, one of the things that makes the DSL15C so cool is that it has a pentode/triode switch for selecting the full 15w or a half 7.5w of output. That’s a great bit of versatility, and long time readers of this blog know that versatility is a big deal here.

The DSL15C also features a foot switchable gain channel that lets you switch between classic gain and ultra gain. Also present is a “deep switch” that gives your tone a bit of a low end boost.

With all these features and a 12 inch Celestial G12E speaker and built in reverb, the DSL15C captures the classic EL84 British sound in a tight little tone package.

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Laney Cub 12

The Laney Cub 12 has a 15w and <1w input. Jack into the 15w input and you get the full throated roar, jack into the <1w and you get a more manageable volume for practice, with substantially less headroom. This means that you can get those dreamy, creamy British overdrive tones that EL84s are known for at a much lower volume.

  • 15 watt all tube class A/B amplifier
  • Three ECC83 tubes in the pre amp and two EL84s in the power amp stage
  • Digital reverb (Tone and volume (as with the Cubs 8 and 10) and bass, middle treble EQ and gain control
  • FX loop
  • 12 inch Celestion speaker

The tube configuration gives the Cub 12 a much bigger voice than the Cub 8 and 10. Also, if 12 inches of Celestion isn’t enough for you, there’s also an external speaker out jack.

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What’s the Difference Between Epiphone and Gibson Guitars?

The debate between Epiphone vs Gibson may seem a lot like the one between Squier vs Fender, but it’s less clear than that. Where Squier guitars are largely less expensive versions of Fender models, Epiphone offers less expensive versions of Gibson models but also many models not found in the Gibson catalog.

History of Epiphone and Gibson

Back in the 1930s Epiphone and Gibson were rivals. They competed in the archtop guitar market and early electric guitars. By the late 1950s Epiphone was giving Gibson so much competition that Gibson purchased Epiphone in 1957.

If you can’t beat ‘em, buy ‘em!

Price difference between Epiphone vs Gibson

In the years that followed the acquisition Epiphone became known for low-end versions of Gibson models. Not long ago many viewed Epiphone as existing solely to make cheap Les Pauls and SGs to compete with the counterfeit versions coming out of China.

This has changed dramatically in recent years. Firstly, Gibson has started offering low cost (for Gibson)  guitars that bear the Gibson name. For example, the Gibson M2 Melody Maker sells for $400, which is well within the price range for an Epiphone guitar. At the same time, Epiphone has started making more expensive models.

For instance, the Epiphone 1965 Elitist Casino sells for $2,000. That sits right in the Gibson sweet spot of pricing yet proudly bears the Epiphone logo. Clearly the companies are trying to blend the images of these two brands. Time will tell if it’s a winning strategy, or just another bungle along the lines of Gibson’s robot-tuner enabled mistakes of 2015.

The final aspect of price is retained value. Gibson guitars retain more of their original value in the used market than Epiphones, generally speaking.

Gibson quality vs Epiphone quality

After price, the most important difference in most hobbyists minds is that of quality.

Which is better quality – Gibson or Epiphone?

Generally speaking, Gibson guitars offer better quality parts and wood but the differences go beyond base materials. Epiphone is known for using a variety of wood types in a single guitar body, while Gibson typically sticks to one. For example, Epiphone might make a body out of less expensive poplar and put a thin maple veneer over it.

The question for the player is whether this makes any difference top the overall quality. Most players, especially hobbyists, don’t notice the difference between tone woods in an electric guitar they way they would in an acoustic guitar.

One other difference between Epiphone and Gibson construction is in the number of pieces of wood used in the body. Both use multiple segments, but Gibson is usually no more than 2 or 3 pieces glued together, where Epiphone can be many more. This leads to the use of a solid veneer to disguise the connection points for a better aesthetic.

Pickups and hardware differences

It’s a good rule of thumb that the cheaper the guitar, the lower quality the hardware it will have. This rule hold true in our comparison of Epiphone vs Gibson as well. Gibson guitars typically have higher quality components.

In fact, the more affordable Gibson models (think the M2 Melody Maker) even use Epiphone ProBucker pickups!

Another rule of thumb is that Gibson guitars come with better stock pickups than Epiphones, but pickups are so easy to swap and those better pickups are baked into the higher price of the Gibsons that it’s hardly a mark against Epiphones.

Bottom Line: Epiphone vs. Gibson

Epiphone gets a bad rap as being a poor quality Gibson, but that’s really no longer true. What is true is that you get better quality with a Gibson guitar, but better value with an Epiphone guitar. If you’re a professional musician or a collector/investor then Gibson is the way to go. But for the other 99%, Epiphone is a fine choice.

Popular Epiphone Guitars
Epiphone-G-310

The G-310 is styled after the Gibson SG, but sells as a fraction of the cost.

The SG is a signature guitar for the likes of Pete Townshend, Eric Clapton, Tony Iommi, Paul Weller, Angus Young and Derek Trucks. The Epiphone G-310 is your chance to own a comparable guitar at an affordable price.

The Epiphone G-310 is built to the same dimensions as the vintage Gibson SGs or the 1960s, and with the same techniques as those used in the original Kalamazoo factory. It’s a well balanced guitar, unlike many cheaper clones that tend to be neck-heavy.

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The Epiphone Dot is capable of producing a wide range of tone that makes it a very versatile electric guitar that’s great for beginners. It’s also a Semi-hollowbody, which means it has an acoustic element to it as well as electric, and has more resonance than a solid body electric guitar.

The Epiphone Dot is well suited to classic rock, country, blues and jazz styles.

The Epiphone Dot is Epiphone’s version of the Gibson ES 335 “Dot” (made famous by the likes of Eric Clapton, BB King, Albert Lee, Chuck Berry, Larry Carlton, Dave Grohl and Roy Orbison) and is one of the best deals today for guitar players who want the classic sound of an ES 335 at an affordable price.

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Popular Gibson Guitars


The Les Paul CM

The CM features a mahogany body, topped with carved maple. The neck is a comfortable, rounded C profile made of maple. It also features Gibson’s controversial “G force” tuning system, which basically tunes the guitar for you in a variety of tunings (Standard, DADGAD, Dropped-D, etc….)

So why is it so cheap?

At less than $1000, the Les Paul CM is a budget Gibson to be sure. The reason you can buy a Gibson so “cheap” is because the quality of wood is considered “C” grade, as opposed to the higher “A” range. All this means is that the wood grain is not as pleasing to the eye. Some people would argue that it affects the sound, but this is debatable on a guitar selling in the sub-thousand dollar price point.

Having a single pickup also helps keep production costs down.

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Gibson Les Paul Tribute, Faded Honey Burst

The Les Paul Tribute is more of what you expect from Gibson. Traditional A-grade mahogany-maple woods. Vintage Keystone style tuners and finish give this guitar the look and feel you expect from a Gibson.

The tone is vintage Gibson as well. The Tribute comes with 2 humbucking pickups : a 490R and a 490T, both with a bit more bite than a standard PAF style pickup.

The Gibson Les Paul Tribute is made in the USA, which also contributes to its price.

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Gibson Les Paul Standard

Here’s a Les Paul standard in beautiful Blueberry Burst finish. The standard is made using AAA-grade flame top maple for that classic “burst” finish, with a blueberry twist. The look may be classic but the electronics are modern. All four of the volume and tone knobs are push-pull, meaning you get even more versatility in pickup tone.

Speaking of pickups.. The Les Paul Standard is decked out in dual upgraded PAF style Burstbucker Pro pickups in the neck and bridge positions.

Upgraded hardware puts the finishing touches on the beauty.

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